Compounds obtained according to this invention are useful for many and varied applications which are evident to the technicians in various industries.
They can be used, for example, as intermediate compounds for the further synthesis of industrial products in the field of organic chemistry in general and with particular regard to the preparation of the so-called fine chemicals, i.e., of products having a wide range of applications in perfumery, phytopharmaceutical products (phenylacetic acid), pharmaceutical products, etc., due to the presence in "alpha" position, in respect of the carboxyester or carboxylic group, of an aryl group which ensures most interesting possibilities of reaction for said compounds.
In particular, the alkyl ester, and by consequence its corresponding free acid, 2-(6'-methoxy-2'-naphthyl)-alphamethyl-acetic acid, which, for the sake of simplicity and exactness, will be hereinafter referred to as 2-(6'-methoxy-2'-naphthyl)-propionic acid, is in the form (+) adapted to use in the pharmaceutical field as anti-inflammatory, analgesic, antipyretic, anti-itching, etc., agent. Such use is widely described in the literature, as well as the relevant pharmaceutical preparations such as solutions, suspensions, pills, capsules, etc., (see, for instance, British Pat. No. 1,211,134).
Because of their versatility, several methods of preparing arylacetic acids have been proposed. For example, they can be prepared from benzyl halides or substituted benzyl halides by alkaline cyanuration and successive hydrolysis of the cyano group. Thus, 2-(4'-isobutylphenyl)-propionic acid, a pharmaceutical product known as "Ibuprofen", is prepared by reacting NaCN with the corresponding benzyl chloride followed by methylation and hydrolysis (U.S. Pat. No. 3,385,886).
Reactions have been described, also, according to which arylacetic acids are obtained by means of rearrangement mechanisms. For example, the Willgerodt reaction is known, in which an alkylarylketone is converted to the amide or the ammonium salt of the corresponding omega-aryl-alkanoic acid by reaction with ammonium polysulphide. In fact, the rearrangement of the aryl groups always occurs on the carbon atom which is farthest from the carbonyl group, and not, as in the process of the present invention, on the carbon atom in alpha position with respect to the carbonyl group. Furthermore, the yields are insufficient for practical purposes and the starting compound is an alkylarylketone instead of a haloketone.
Another rearrangement reaction starting from acylic halides leads to the arylacetic acids by reaction with diazomethane and successive hydrolysis in the presence of Ag.sub.2 O. That reaction comprises the use of diazo-methane and the forming of a diazo-ketone, which are explosive compounds compatible with difficulty with a practical industrial process. Besides, the reaction is described as being irregular and providing variable yields.
The rearrangement of alkylarylketones to methyl esters of arylacetic acids by means of thallium salts has been described, but also in this case the method cannot be considered as interesting from the practical, commercial viewpoint due to the high toxicity of the thallium salts employed.
The mechanism of the dehalogenation of 1-benzoyl-1-bromo-cyclohexane by means of AgSbF.sub.6 in alcohols, which leads to an ethylene ketone and in part to a transposition ester 1-phenyl-1-carboxyalkyl-cyclohexane, has also been described. That is the study of the dehalogenation of a particular tertiary aryl alpha-haloketone, while, on the other hand, it has been explicitly stated in literature that in the presence of primary or secondary alpha-haloketones no rearrangement reactions catalyzed by silver ions in alcohols occur.
Finally, the obtainment of 2-methyl-2-phenylpropionic acid by rearrangement of alpha-bromoisobutyrophenone with AgClO.sub.4, either in the presence or in the absence of perchloric acid has been described. The description deals with the mechanics of the process, and also explicitly states that the rearrangement does not occur with primary and secondary alpha-haloketones independently of the presence of the perchloric acid, but only with the tertiary alpha-haloketone.
The previously known methods summarized herein, and in particular in British Pat. No. 1,211,134, are different from the present method and have few possibilities of use on an industrial scale due to the plurality and/or complexity of the required production steps, or the sophistication of the starting materials, or the generally relatively low yields.